The device of the present invention directly derives and complements several inventions owned by applicant, the first configuration having been filed with Brazilian Patent Office on Aug. 21, 1978 (PI 7805402-8), the second on Sep. 9, 1985 (PI 8504326-5), the third on Feb. 5, 1991 (PI 9100456-0), the fourth on Nov. 5, 1993 (PI 9304495-0), the fifth on Mar. 27, 1996 (PI 9601145-9), the sixth on Mar. 23, 2009 (PI 0902183-3), and the last on Jun. 20, 2016 (BR102016014526-0)
The first configuration (basic structure) is defined by parts 1—Upper/Lower Chord, part 11—Web diagonals, part 12—Lateral Bracing, part 15—Roof Steel Coil (tile), part 8—‘Cover plate’.
From its launch to the present days, the system initially revealed, described above, has about 10 million square meters installed, meeting all the demands and technical requirements requested by the market.
As is generally known, however, the climate is constantly changing throughout the world, changing the scenario of temperatures, rainfall and wind. Nowadays, many of the climate changes are caused by the phenomenon “El Niño” causing droughts or flooding, extreme cold or extreme heat, often in areas that have never experienced such weather conditions.
In the case of wind, it is noted a gradual and constant increase in local average speeds, implying greater pressures to be resisted by the buildings in general, and specifically by roofs and coverages.
Thus, in places where the wind conditions are highly unfavorable, some cases of displacement and even removal of part of coverages were observed. In the case of the object of present invention, displacement and removal of one or more Roof Steel Coils (tiles) were observed.
As shown in FIGS. 1, 2A and 2B, the Roof Steel Coil (15), which acts as a tile in the coverage structure of the present invention, is resiliently contained between the Upper Chord (1) and the Cover plate (8) in its transverse ends (see FIG. 1), without a proper attachment (bolt, rivet etc.) despite the efficient result obtained by the characteristic constructional form of said coverage structure.
For a better understanding of this, a study was made based on Elastic Stability Theory, which clarified the operation of the Roof Steel Coil (tile) (15).
By this theory, the deformation of the Roof Steel Coil (15) caused by a radially distributed stress (FIG. 5) always starts with an inflection point near its center (C), as shown in FIGS. 3 and 4.
However, the theory is difficult to apply since the form and conditions of the theoretical model do not accurately reflect the reality and peculiarities of the coverage to which the object of the present invention is applicable.
Therefore, it was decided to carry out assays for the solution of the problem.
In said tests it has been evidenced that the Roof Steel Coil supports the wind pressure due to its shape and also that its deformation takes place exactly as studied theoretically, that is, deformation of the Roof Steel Coil (tile) has been observed, caused by a distributed stress, started an inflection point near its center (C), as shown in FIGS. 3, 4 and 5.
In a way like the theoretical one, upon deforming, the Roof Steel Coil loses its strength and tends to come out of the support structure, since it is resiliently contained between the Upper Chord (1) and the Cover plate (8) in its transverse ends, keeping the inflection point at the center of the coil (C), as shown in FIG. 4.
Hence, the present invention has been developed, more specifically, a Wind uplift strap (30) which alters the method of securing the Roof Steel Coil (15) of the initially disclosed system, increasing its relative strength.